The ventilation of confined spaces can be controlled according to demand by using CO₂-concentration as an indicator for occupancy. This is realised by a feedback loop involving CO₂-sensors and ventilation equipment allowing for power variation.

This principle is applicable to railway coaches:

Most of today's passenger coaches are ventilated according to seating capacity rather than actual demand (number of passengers), resulting in a constant outside air intake of some 20 m³ per hour and seat or 1600 m³ for a 80 seat coach. A CO₂-controlled operation may considerably reduce these figures while ensuring air quality. This saves energy since less outside air has to be heated or cooled to inside temperature.

Fields of application

• Buildings with a high variation of occupancy and high occupancy peaks, such as cinemas, theaters, classrooms, meeting rooms and retail establishments.
• Railways